The present invention relates to an improvement in a continuous forming, filling and packing apparatus.
Recently, foods such as jam, marmalade, cream and yoghurt etc. packed in small containers have become popular because of the ease of handling and in view of sanitation. For example, each food package often contains an amount of food necessary to satisfy one use or individual serving, and this will be referred hereinafter as to a "portion pack" when applicable.
FIGS. 1 and 2 illustrate conventional packages for food material and FIG. 1 is a perspective view while
FIG. 2 is a cross-section taken along a line II--II in FIG. 1. A container portion 1 is made from a bottom sheet 2 of thermoplastic resin. The container portion 1 is filled with a food 3 such as jam, marmalade, cream or yoghurt. A cover portion 4 is constituted usually by a lamination of an aluminum foil and a thermally fusible resin layer. After the food 3 is placed in the container portion 1, the cover sheet 4 is placed over the opening of the container portion 1 and seals the latter by being thermally fused thereto. On an uppper surface of the cover sheet 4, a set of symbols for indicating the contents, the trade name thereof, the trademark, and the manufacturer thereof etc. (hereinafter, referred to as "symbol F" when applicable) are printed.
The usual practice is to manufacture the portion packs in a batch. For example, an array of 2.times.3 portion packs may be manufactured in one cycle. Therefore, the cover sheet 4 has a corresponding number of printing sets of the symbol F thereon. In FIG. 3 a reference numeral 5 indicates a reading mark which is used to control the apparatus to obtain a correspondence in postion between the symbol F on the cover sheet 4 and the container portion 1 as will be described later. The sparing or pitch of the reading marks 5 together with the symbols F may include some error which may be caused by some problem in printing preciseness. An accumulation of the errors will cause a considerable divergence between the container portion 1 and the symbol F on the cover sheet 4. Examples of such divergences are illustrated in FIGS. 4a to 4c in plan view and in FIGS. 5a to 5c in cross section, respectively. With such divergence, the portion packs are shabby and the values thereof are lowered.
In FIG. 6 a conventional apparatus for manufacturing packaged food material is shown, wherein a reference numeral 11 indicates a roll of the thermoplastic bottom sheet material 2 and 12 indicates a roll of the cover sheet material. A heating device 13 serves to heat the bottom sheet 2 and includes a pair of heat plates between which the bottom sheet 2 is passed so as to be heated to a suitable temperature.
A forming device 14 for shaping the bottom sheet 2 into containers having suitable shape after heating of the bottom sheet 2 is provided upstream of a filling device 15 serving to fill the containers 2 formed by the forming device 14 with a predetermined amount of food such as jam.
A sealing device 16 functions to seal the containers 2, each filled with a predetermined amount of food, with a laminated cover sheet 4 comprised of a lamination of aluminum foil and a thermally fusible resin layer.
The cover sheet 4 is pressed towards the open container with the resin layer side facing downwardly onto the openings of containers 2 by using a heat plate supported for vertical movement by a frame structure (not shown) to fuse the resin layer to the peripheries of the openings and then cooling the fused assembly.
A reading device 17 functions to read photoelectrically the marks 5 shown in FIG. 3 and sends an output signal to a control device (not shown).
The reading may be performed in such a way as shown in FIGS. 7a and 7b. The reading device 17 is initially set such that a center S of a light spot emitted therefrom coincides with a position prior to a trailing edge T of the mark 5 by .DELTA.Q, as shown in FIG. 7a.
When the marks 5 are printed closer together than they should be, the accumulated error after several to several tens of cycles produces a positional relation shown in FIG. 7b between the trailing edge T of the mark and the center S of the light spot from the reading device 17. By making the reading device 17 capable of discriminating the printed colour of the mark 5 from the colour of the background, the reading device 17 discriminates the condition shown in FIG. 7b and sends a signal through the control device to a carrying device 18 to correct the feeding amount of a product 6 composed of the containers sealed with the cover sheet 4 as to be described.
The carrying device 18 functions to pull intermittently the containers 2 sealed with the cover sheet 4 by the sealing device 16 in synchronism with the feeding pitch.
The conventional carrying device is shown in more detail in FIGS. 8 and 9 wherein grippers 31A and 31B associated with an air cylinder pinch the product 6 in response to a carrying signal. A slide block 32 on which the grippers 31A and 31B are mounted is guided by guide bars 33 and driven back and forth by a driving device 34 having an air cylinder. A plate 35 is provided for correcting the feeding amount of the product. The plate 35 has a thickness in the order of .DELTA.Q and is guided by a guide 36 and driven vertically according to demand by a driving device 37 having an air cylinder.
When the positional relation between the printed mark 5 on the cover sheet 4 and the mark reading device 17 becomes as shown in FIG. 7b, the reading device 17 produces an output signal which is fed to the control device not shown. Then, the driving device 37 is actuated in response to an instruction from the control device to move the plate 35 upwardly. In this state, the grippers 31A and 31B grip the product sheet 6. By pulling the slide block 32 by the driving device 34, the amount of stroke is reduced by a distance corresponding to the thickness of the plate 35, comparing with that when the plate 35 is in the bottom position.
Therefore, it is possible to correct the carrying amount correspondingly to the accumulation of the printing errors.
In FIG. 6, a punching device 19 is shown which functions to punch the respective portion packs shown in FIG. 1 out from the product sheet 6 by using a combination of a male and female edges supported for vertical movement by the frame (not shown) of the apparatus. The products H punched out from the product sheet 6 are discharged by an ejection device (not shown) to a predetermined location.
A take-up device 20 is provided which functions to receive waste 7 after the punching performed by the punching device 19.
As described with reference to FIGS. 6 to 9, the conventional forming, filling and packing apparatus manufactures the portion packs H by performing the steps of heat-forming the container portions 2 of the thermoplastic resin, filling them with materials 3, sealing the containers with the cover sheet 4, punching the packs out from a web and then taking up the waste, together with the step of correcting the carrying amount of the sheet materials. With using this apparatus, however, the appearance of the final products are frequently degraded as shown in FIGS. 4 and 5.
That is, FIGS. 4a and 5a show an example in which the cover sheet 4 seals the container portion 2 with the symbol F printed thereon deviated from the container portion 2.
FIGS. 4b and 5b show another example in which the punching of the packs H from the web is performed erroneously causing the flange portion 8 of the pack to be unbalanced. If the punching operation is made with more deviation than that shown in FIGS. 4b and 5b, a portion of the flange in one side will be lost causing a leakage of the contents 3 of the container.
FIGS. 4c and 5c show a further example in which the flange portion is stamped by a circular male die to prevent air from being introduced in the container to thereby clearly improve preservation of the contents but the stamping is made erroneously causing a stamped recess 9 which is off-centered. If the recess is off-centered more than the above, the circular stamp may be out of the flange 8 of the container.
The reasons why these states may be caused are as follows: (1) The state shown in FIGS. 4a and 5a may be caused by an erroneous selection of the setting position of the mark reading device 17.
As shown in FIG. 6, a temporary reference position is indicated in a center X--X of the sealing portion of the sealing device 16 and the distance L.sub.L between the center S of the light spot from the reading device 17 and the center X--X is not equal to the distance L.sub.B between the center of the forming portion of the forming device 14 and the center X--X. There is, in fact, a considerable difference between L.sub.L and L.sub.B. Therefore, even if the correction control of the carrying amount is performed, it only corrects the printing error of the cover sheet 4. It does not make any control so that the symbol F of the cover sheet 4 coincides with the formed container 2.
(2) The state shown in FIGS. 4b and 5b is caused by having no position correction for the punching operation by the punching device 19. Even with the carrying amount correction control, punching may be performed at an erroneous position due to the lack of the positional control of the punching.
(3) The state shown in FIGS. 4c and 5c is caused by having no position correction of the sealing operation performed by the sealing device 16.
Although the spacings of the marks printed on the cover sheet 4 usually are in error by an amount smaller than a reference spacing P.sub.o, this is not always true and there may be cases where the actual spacing P.sub.i is larger than the reference spacing P.sub.o. That is, the case where P.sub.o -P.sub.i =.DELTA.P.sub.i &lt;O can be considered. In this case .SIGMA..DELTA.P.sub.i is negative which shows the state where the center S of the light spot is shifted from the state in FIG. 7a to the end E of the mark 5.
In this case, since the mark reading device 17 does not detect the mark 5, the carrying in the next cycle will be made by P.sub.o -.DELTA.Q according to the above mentioned carrying amount correction, which may cause the deviation to be more increased.
In view of the above, it may be considered to add a discriminating function to the mark reading device.
That is, it is possible to make the size of the mark 5 no larger than 2.DELTA.Q and to initially set the position of the reading member of the mark reading device at a center of the mark.
Therefore, when .vertline..SIGMA..DELTA.P.sub.i .vertline.&gt;.DELTA.Q, it becomes impossible to detect the mark by the mark reading device and thus the feeding of the cover sheet 4 is stopped.
The discriminating function is to decide whether the cover sheet should be stopped after a detection of the mark by the mark reading device or before the detection.
The former case corresponds to .SIGMA..DELTA.P.sub.i &gt;.DELTA.Q and the latter case corresponds to .SIGMA..DELTA.P.sub.i &lt;-.DELTA.Q. Therefore it is enough to correct the carrying amount of the cover sheet 4 to P.sub.o -.DELTA.Q or P.sub.o +.DELTA.Q in the preceding cycle.
The case where the carrying amount is to be increased may be handled in the same manner as shown in FIGS. 8 and 9.
However, the addition of the discriminating function to the mark reading device may considerably increase the cost.
In the apparatus shown in FIG. 6, when the sealing device 16 and the punching device 19 are not in appropriate positions, respectively, even if the symbols on the cover sheet 4 correspond exactly in position to the container portions 2, the appearance of the product H will be degraded. Therefore, it is necessary to provide other mark reading devices for the sealing device 16 and the punching device 19, respectively, so that the sealing device 16 and the punching device 19 can be moved in response to output instructions produced by these additional reading devices, respectively. This may cause the same disadvantages as those encountered previously.